Word retrieval difficulty is the most common symptom observed in people with aphasia, having a profound impact on individuals'ability to communicate in daily life. While it has long been acknowledged that adequate processing of meaning or "semantic knowledge" is a necessary precursor to accurate word retrieval, it remains unclear how deficient processing of semantic knowledge influences word retrieval difficulties observed in aphasia. The long-term goal is to design semantically-based treatments for word retrieval impairment in aphasia that maximize the types of semantic information that are utilized to facilitate word retrieval. The overall objective of this project is to determine the relationships among semantic feature knowledge, word retrieval deficits, and lesion location in individuals with aphasia. The central hypothesis is that (1) deficient processing of specific semantic feature cues will differentially impact word retrieval for concepts whose meanings are weighted in favor of those features;and (2) deficient semantic feature/concept processing is associated with lesion location. The rationale for the proposed project is that understanding the relationship between semantic knowledge and word retrieval impairment in aphasia will provide the foundation upon which to expand clinical research into theoretically-motivated assessment and treatment of deficient semantically-guided lexical retrieval. The central hypothesis will be tested by pursuing the following two specific aims: (1) Determine the association between semantic feature cues and word retrieval for different types of object concepts, and (2) Determine the extent to which semantic feature/concept processing is associated with lesion location in aphasia. To pursue these specific aims, individuals with aphasia will be assessed using a neuropsychological battery designed to provide for direct comparison between feature types within the same living and nonliving objects. High resolution MRI scans will be collected for participants with aphasia and behavioral performance will be related to lesion location. Once this information has been obtained, it will be possible to differentiate patterns of performance and discern the extent to which semantic feature treatments may be tailored to meet the needs of individuals with differing underlying mechanisms of word retrieval impairment. Furthermore, identifying the interaction between semantic feature and object concept processing will inform ongoing theoretical debates regarding whether impairment to processing of different types of object concepts is an emergent property of feature-processing deficits that can be linked to lesion location. PUBLIC HEALTH RELEVANCE: The proposed research will have an important positive impact on understanding of how best to design theoretically-motivated clinical tools to remediate word retrieval impairment based on knowledge of individuals'ability to process semantic feature cues. The proposed project has relevance to public health because the mechanisms to be investigated will inform the development of assessments and treatments for word retrieval impairments that can compromise communication in the daily lives of individuals with aphasia.